Flexible mandrels for bending wave guides



Jan. 22, 1957 F. J. FUCHS, JR

FLEXIBLE MANDRELS FOR BENDING WAVE GUIDES Filed Dec. 18 1951 3 Sheets-Sheet l INVENTOR flAW,

ATTORNEY Jan. 22, 1957 F. J. FUCHS, JR 2,778,402

FLEXIBLE MANDRELS FOR BENDING WAVE cums Filed Dec. 18, 1951 s Sheets-Sheet 2 k r U INVENTOR fi'amds' Jmikj; J1

. BY RAW.

ATTORNEY Jan. 22, 1957 F. J. FUCHS, JR 2,778,402

FLEXIBLE MANDRELS FOR BENDING WAVE GUIDES Filed Dec. 18, 1951 3 Sheets-Sheet 3 L7. 19 4/ 4:7 %7 :5 J fi o pip t37--4 Q 2 H u 11 IN\/ EATOR I l a I l I I 1 I f I BY Z/s..W

ATTORNEY g 2,778,402 c p nted Jan. 22, 1957 FLEXIBLE FOR BENDING -WAVE GUIDES Francis J. .Fuc'hs, Jr., Winston-Salem, N. C., assignor to Western Electric Company, Incorporated, New York, N. Y.,a corporation of New York Application December. 18, 1951, SerialxNo. 262,246

13'Cla'ims. (CL 153-63) This invention pertains tomandrels for'bending hollow bodies, and more particularly to flexible mandrels used in bending waveguide :tu'bing.

In bending hollow bodies ortubes, large tensile and compressive stressesare developed within the walls ofthe tube which may cause buckling or collapse at the ,p'lace of bend; this is particularly true in drawbending'where the tubing is'drawn over a mandrel between a pressure die and a wiping die where high 'pressures are exerted externally'againstthetubing. In orderto overcome'buckling and other-difiiculties and'to accurately maintain the internal dimensions or the tube, the walls thereof must -be supported from the inside by a mandrel. Further, the end of the supporting mandrel must be flexible -so that it may bend with the tube and' be easily extracted after the bending opcration is completed. 'Moreovergthe supporting mandrel should have a smooth, hard, and continuous surface :so that it "-will .keep :the internal walls of the bent tubeismooth and:preventiflattening and wrin- -kling.

An object .of this invention is eto provide :asatisfactory rmandre'l which :will support "the internal walls of a tube during bending to keep the walls 'smoothandzmaintain the internal dimensions'thereof.

A further 'object of the invention is to providea :low cost mandrel of -sturdy and simple .construction to quickly vary the .length thereof in making diiferent types =of "bends.

Otherobjectsand-advantagesof the invention will\be- .coine apparent :from the following description and *the accompanying drawings wherein:

. Fig. V1 is -.a longitudinal .section .of wave guide itubing being bent with an interlocking ring mandrel inserted therein whichlis a,preferred-emhodiment of :the invention;

Fig. '2 is a front elevational view of the inter-locking ring-mandrel showninFig. .1;

,Fig.'3 -.is aplanview of thislinterlookingring mandrel; Fig. 4 -is an enlarged .cross section .taken along line 4-40'f Fig. '2;

Fig. '5 is an exploded perspective view of the interlocking ring mandrel s'hownlinFigs. 1 to'9., inclusive;

Fig. "6 is an enlarged front elevational viewof three of the interlocking links or rings of the mandrel shown in ig- Fig. '7 is a longitudinal section of these three interlocked links taken along line 77 io'f'Fig. 6;

"Fig. v8 is an :end elevation of one o'f'the interlocking rings orlirikss'hown' inFig.'"5;

Fig.9 'is an eiilargedperspective view ofthesamering orliiik.showninFigf8;

Fig. "'10 is a frorit elevational view of another-embodiment of a fiexiblemandrel disclosing an interleavedilink construction;

Fig. I11 isaplan view partly insection.taken'alongiline 1'1-11 of'Fig. IO; 7

'Fig. 12 is afragmentaryfront view of a modification of the interleavedimandrel;

Fig. 13 is along'itudinal section of the modified interleaved mandrel taken along line 13-13 ofFig. '12;

Fig. ]14.is a. front: elevation of another modification of an interleaved mandrel;

Fig. I1'5 isa plan-view of the mandrel shown in Fig. .14;

Fig. .16 -is a "fragmentaryfront elevational view ofstill another modification of an interleaved mandrel;

Fig. 17 .is a ,plan view of-the mandrel shownin Fig. 16;

Fig. 18 is a'front elevation, partly in section, of another embodimentof afiexible mandrel showing a. pivoted disk arrangement 'with an endless flexible steel band there- 'about, and

Fig. 19 is an end view of the embodiment shown in Fig. 18.

ln'the drawings and throughout "the specification, like reference numerals are employed to designate similar 'parts.

keferring n'ow to'the drawings, attentionisfirstdirected to *Figs. 1 to '9, inclusive; which illustrate a preferred embodiment 'of an interlocking ring mandrel comprising 'a rigid rrectangular-stem'zll (Figs. 1 *and'2) made of two rectangular steel strips 2 1 (Figs. 3 and '5) a'ndhav'ing a flexible body 22 :attached -thereto. Each of the "two "sections 21 of the stem has a'curved end 23 which is so contoured to provide an inden'ted semicircular portion having'a cylindrical aperture 24"therein. The semicircular "end portions 23 of the two strips 21 face each other to form a recess 24 'for receiving an end 'of the flexible b0dyi22. I

trhe flexible bodyf22 consists of two series of interlocking :rings 26 of rectangular cross isection. Each-of the rings :26 is \detachably connected toi'ts adjacent ring, :and the .ring adjacent :the :recess 24 in the :strip 21 of .thestem -20'is detachably connected thereto. Each ring 26 has .a radius equal :to that of the cylindrical recess 24 at the-end of .the'strip 2-1. :Also'each :ring .or link '26 has therein a central cylindrical aperture 27 of-the same radius as :the apertureZS in thestem v20 or equal -to-ione half the radius of .the external periphery :of'the ring 26.

One side of each ring has an .arcuate groove-or recess .28 therein whose bottom surface is half way between the sides and is perpendicular to .the longitudinal axis :of 'thetring and is definedby arcs 29 and 30 (-Fig-s.6-and.9-) of two concentric circles. that have their centers on the externalperiphery of the ring and form the boundary er a laterally extending tongue 75. The .radius of the smaller arc 29 is equal to the radius of the aperture 25 or the aperture 27 and the radius of the larger are 30 is equal to'theradius of the periphery of the ring.

The other side of the ring'26 has a-notch 31 (Figs. 5 and "9) 'thatis'diametrically opposite the arcuate groove -28 and'thetongue'7'5. The bottom surface of the notch '31 is half way between the flat sides of the ring and-is perpendicular to'the axis of the ring. The upright walls of this notch are defined by "the arcs 32 and 33 (Fig. 6) of two circles,'both equal in radius tothat of the external periphery of the ring. Are 32 has its radial center at sconstruction, while "the other-half of the 'rings has the notch constructionwith the positions of the arms 32 and 3'3 interchanged.

The interlocking of the rings 26 is efiectedbyplacing "in the arcuate groove '28 .of one ring, the portion 34 (Fig. 7.) of the wall of the adjacent ring that is above its notch '31 so that the "tongues it into the central apertures 27. "Thus the series of rings 26 are interlocked 'to'form a fiexible 'body. "The end 23 of-a strip-zl'is then placed so that it nests within the arcuate groove 28 of series of detachable rings thus supports each other and maintains the nested interlocked relationship thereof.

A continuous flexible thin steel strip 36 (Fig. 2) having its ends attached to the stem is placed over and around the interlocked rings or links 26 forming the flexible body 22 to engage the inner walls of the tubing (Fig.

1) being bent to prevent scoring or marking by these links.

Attention is next directed to Figs. 10 and ll which illustrate a second embodiment of a flexible mandrel. In this form, the mandrel comprises a rigid stem 37 having a flexible body 38 connected thereto, and a continuous flexible metal strip 39 secured thereto by screws 40 and hold down inserts 41. The resilient strip 39 covers the end and the portions of the mandrel that support the Walls of the tube during bending. The flexible body 38 consists of interleaved plates 42 arranged in overlapping rows with the center lines of the plates of one row aligned with the edges of the plates in an adjacent row and connected by suitable pivot pins 43. Grooves between forks in the end of the stem 37 receive the adjacent end plates of the flexible body 38 which is attached to the stem 37 by a pivot pin 43 passing through the end forks of the stem and the end plates 42. Each plate 42 of the flexible body 38 is hexagonal in shape with an arcuate side 45 of the plate supporting the wall of the tube that is in tension during bending. Spacers 46 retain the separation between the outer end links 47. The flexible strip 39 is formed tightly around the end links 47 and over and under the flexible body 38 of the mandrel that support the walls of the tube during bending.

Figs. 12 and 13 illustrate a modification of an interleaved mandrel. This modified mandrel comprises a rigid stem 48 having a curved, forked, and truncated end with an aperture 49 (Fig. 13) therethrough. Plates 50 having curved sides are interleaved with the plural forked end of the rigid stem 48 and are conected thereto by a pivot pin 51. Arcuate end link 52 is loosely connected to the plates 50 by a pivot pin 53 passing through a large aperture 54 in the end link 56. Also a steel flexible band like that in Fig. 10 may be fastened to the stem 48 and passed over and around the links 50 and 52.

Figs. 14 and 15 illustrate another modification of an interleaved mandrel comprising a rigid stem 55 having the upper and lower surfaces of its forked end 56 shaped according to the contour of a desired bend. A forked link 57 is interleaved with the stem 55 and is pivotally connected thereto by a pivot pin 58. The forked link 57 has its upper surface 59 and its lower surface 60, that support the walls of the wave guide tubing during bending, curved to correspond to that of the forked end 56 and to the radius of the bend desired in a piece of tubing. Here again a flexible steel strip may be secured to the stem 55 and pass over and under the links 56 and 57 to assist in producing a smooth bend.

Figs. 16 and 17 illustrate still another modification of an interleaved mandrel comprising a rigid stem 61 with a notch in one end and having a link 62 pivotally connected therein by pivot pin 63. A slotted end link 64 straddles link 62 and is pivotally connected thereto by the pin 65. A flexible steel strip may be secured to the stem 61 and pass over and under the links 62, 64 to prevent scoring of the inside of the tube being bent.

Figs. 18 and 19 illustrate another embodiment of a tube bending mandrel that comprises a support 66 having a bifurcated end 67 in which an end 68 of a rigid member 70 is pivoted on a pin 69. A socket 72 in the other end of the member 70 is rectangular at its base, but has curved Openings or recesses 73 that are adapted to receive a pivot disk 74. This disk pivots in the socket 72 and a threaded pin 75 passes through the center of the disk parallel to a face thereof. The pin 75 is also threaded into an end disk 76 parallel to a face of the disk, but offset from the center thereof. The end disk 76 has a recess in one portion that is adapted to receive or nest on the pivot disk 74. Since the end disk 76 is rigidly attached to the pivot disk 74 by the pin 75, the two disks will turn together during a bending operation. The disks 74 and 76 and socket 72 are so arranged that the pivoting is in the plane of bending. An endless flexible belt 77 covers the portion of the disks 74, 76 and member 70 that contact the walls of the wave guide tubing during bending to prevent scoring and assist in producing a smooth bend.

Although the invention has been described with references to a number of particular embodiments, it is to be understood that various modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A mandrel for bending hollow members comprising a rigid stem, a flexible body comprising a plurality of centrally apertured overlapping rings having arcuate projections being slidably movable within the overlapping portion of the apertures of adjacent rings, means for detachably connecting an end of the flexible body to an end of the stem, and a flexible strip having its ends secured to the stem and passing over the flexible body and around its free end and thereunder.

2. A mandrel for bending hollow members comprising a stern, a flexible body of apertured links having peripheral projections slidable in apertures of adjacent links, means for connecting one end of the flexible body to the stem, and a continuous flexible band having its ends secured to the stern and passing over the body and around its free end and thereunder.

3. A mandrel for bending tubing comprising a stem, a flexible body of a plurality of apertured interlocking ring-like links, a continuous spring steel strip passing over and under the flexible body, and means for securing the ends of the continuous strip to the stem.

4. A mandrel for bending tubing comprising a stem, a flexible body consisting only of a series of detachably interlocking elements, means for pivotally connecting one end of the flexible body to the stem, a continuous spring steel band passing over the body and around its free end and thereunder, and means for securing the ends of said strip to the stem.

5. A tube bending mandrel comprising a pair of complementary rigid stems, a plurality of detachably interlocking elements forming a pair of mutually supporting complementary flexible sections, means at an end of each of the rigid stems for detachably securing an end of one of the flexible sections thereto, and means for securing the pair of rigid stems together to bring the flexible sections into complementary cooperation to form a flexible body having the form and dimensions of the inside of a tube to be bent.

6. A tube bending mandrel comprising a pair of complementary rigid stems, a plurality of detachably interlocking elements forming a pair of mutually supporting complementary flexible sections, means at an end of each of the rigid stems for detachably securing an end of one of the flexible sections thereto, means for securing the pair of rigid stems together to bring the flexible sections into complementary cooperation to form a flexible body having the form and dimensions of the inside of a tube to be bent, a spring steel strip passing over the flexible sections and around the free ends thereof and thereunder, and means for securing the ends of the strip to the pair of stems.

7. A mandrel for bending tubing comprising a stem, and a flexible body having one end attached to the stem, said flexible body including a series of detachable interlocking rings having central openings, each ring having on one side a pair of arcuate recesses and a tongue, the other side of each ring having an arcuate recess diametrically opposite the said tongue, the tongues fitting into the central openings of adjacent rings and portions of adjacent rings fitting into the said recesses.

8. In a tube bending mandrel, a rigid stem, a series of interlocking movable elements having central apertures, means for securing an end element of the said series to an end of the stem, and means for detachably interlocking said elements together comprising a tongue extending laterally from one side of each element and grooves about said tongue, a recess in another side of each element and opposite the said tongue, the said tongues fitting into the central apertures of adjacent elements and portions of adjacent elements interlocking in the said grooves and recesses thereof.

9. In a tube bending mandrel, a series of interlocking movable rings having central apertures, and means for detachably securing said rings together to provide a mandrel of any desired length comprising an arcuate tongue extending laterally from one side of each ring and arcuate grooves about said tongue, a recess on the other side of each ring being bounded by arcuate walls having different centers of radii, the said tongues nesting Within the said central apertures of adjacent rings and portions of said rings nesting within the said grooves and recesses of said rings.

10. In a tube bending mandrel, a series of interlocking elements, each of said elements having a central aperture, a tongue smaller than the said central aperture and on one side of the element and extending from an edge thereof to recesses in the element, said recesses being on the same one side and conforming to the peripheral contour of each element, and an opposite side of each element having another recess conforming to the peripheral contour of each element.

11. In a tube bending mandrel, a rigid stern, a flexible body, end means for connecting an end of the flexible body to said stern, said flexible body comprising overlapping rows of a series of links, pivot pins for interconnecting the rows of links into a cooperative flexible unit, a flexible metal strip passing over and around the free end of the flexible unit and thereunder, and means for securing the ends of the strip to the stem.

12. A tube bending mandrel comprising a rigid stem, a flexible body consisting of a plurality of parallel rows of overlapping links, means for connecting together the overlapping portions of said links, means for connecting the flexible body to the rigid stern, and a flexible metal strip passing over and around the free end of the flexible body and secured at both ends to said stem.

13. A mandrel for supporting the interior of hollow members during a bending operation comprising a rigid stem, a flexible body, and means for detachably connecting one end of the flexible body to an end of the stem, said flexible body being variable in length and consisting only of a series of detachable apertured interlocking elements of ring-like cross section in a plane parallel to the longitudinal axis of the mandrel and having projections which extend laterally from the annular body portions thereof and into slidable engagement with the apertures of adjacent links.

References Cited in the file of this patent UNITED STATES PATENTS 166,293 Orum Aug. 3, 1875 406,992 Burgoin July 16, 1889 1,075,045 Lewis Oct. 7, 1913 1,575,928 Mueller et a1 Mar. 9, 1926 1,654,697 Mueller et a1 Jan. 3, 1928 1,683,573 Mueller et a1 Sept. 4, 1928 2,119,875 Carl June 7, 1938 FOREIGN PATENTS 5,019 Great Britain of 1885 532,068 France Nov. 7, 1921 

